1. Field of Invention
The field of invention relates generally to the fields of material processing and semiconductor integrated circuit manufacturing and, more specifically but not exclusively, relates to correction of systematic errors or non-uniformities through location specific processing using gas cluster ion beam (GCIB) technology.
2. Description of Related Art
Gas cluster ion beam (GCIB) technology has been demonstrated as a useful processing technique for modifying, etching, cleaning, smoothing, and forming thin films on workpieces, including microelectronic workpieces. For purposes of this discussion, gas clusters are nano-sized aggregates of material that are gaseous under conditions of standard temperature and pressure. Such gas clusters may be formed by the condensation of individual gas atoms (or molecules) during the adiabatic expansion of high-pressure gas from a nozzle into a vacuum, and they may consist of aggregates including a few to several thousand atoms/molecules, or more, that are loosely bound together by weak interatomic forces referred to as Van der Waals forces. The gas clusters can be ionized by electron bombardment, which permits the gas clusters to be accelerated using an electric field to form directed beams of controllable beam energy.
Irradiation of a workpiece by a directed GCIB of controllable energy may be used to treat the workpiece according to a dose that is specific to the location on the workpiece. The technique is oftentimes referred to as location specific processing (LSP), wherein the treatment dose or dwell time of the GCIB is varied across the workpiece by adjusting the scan speed. Therefore, one location on the workpiece may be processed differently than another location.
Several emerging applications for GCIB processing of workpieces on an industrial scale exist for semiconductor/microelectronic device fabrication. At present, with continued dimensional scaling in advanced CMOS (complementary metal oxide semiconductor) logic, the requirements for dimensional variability control are concurrently increasing. For multiple technology nodes, advanced control using variable lithographic exposure across wafer has been used to help control critical dimensions in the plane of the wafer. Until the 22 nm (nanometer) node, the most critical dimensions in the vertical dimension have been well controlled by a single deposition or oxidation step. However, with the implementation of replacement metal gate (RMG) techniques and FINFET (fin field effect transistor) structures, some critical dimensions, such as fin height and gate height, are affected by a combination of deposition, CMP (chemical mechanical planarization), and etch steps, requiring a new strategy for precision feature height control. Gas cluster ion beam (GCIB) technology offers precise correction of feature height non-uniformity using LSP algorithms.
Yet, in addition to correcting the non-uniformity present on the workpiece, the implementation of GCIB processing must also correct errors caused by system and/or equipment specific process anomalies that repeatedly affect the output process parameters of a GCIB apparatus. To improve LSP corrective capability, the systematic error for the GCIB processing system must be determined using sacrificial workpieces, which is costly and time intensive.